• Journal of Communications and Networks
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• v.16 no.5
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• pp.548-558
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• 2014

Load distribution is vital to the performance of multipath transport. The task becomes more challenging in real-time multimedia applications (RTMA), which impose stringent delay requirements. Two key issues to be addressed are: 1) How to minimize end-to-end delay and 2) how to alleviate packet reordering that incurs additional recovery time at the receiver. In this paper, we propose sub-packet based multipath load distribution (SPMLD), a new model that splits traffic at the granularity of sub-packet. Our SPMLD model aims to minimize total packet delay by effectively aggregating multiple parallel paths as a single virtual path. First, we formulate the packet splitting over multiple paths as a constrained optimization problem and derive its solution based on progressive approximation method. Second, in the solution, we analyze queuing delay by introducing D/M/1 model and obtain the expression of dynamic packet splitting ratio for each path. Third, in order to describe SPMLD's scheduling policy, we propose two distributed algorithms respectively implemented in the source and destination nodes. We evaluate the performance of SPMLD through extensive simulations in QualNet using real-time H.264 video streaming. Experimental results demonstrate that: SPMLD outperforms previous flow and packet based load distribution models in terms of video peak signal-to-noise ratio, total packet delay, end-to-end delay, and risk of packet reordering. Besides, SPMLD's extra overhead is tiny compared to the input video streaming.

• Journal of Communications and Networks
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• v.18 no.1
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• pp.105-111
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• 2016

Trust models in the literature of MANETs commonly assume that packets have different security requirements. Before a node forwards a packet, if the recipient's trust level does not meet the packet's requirement level, then the recipient must perform certain security association procedures, such as re-authentication. We present in this paper an analysis of the epidemic broadcast delay in such context. The network, mobility and trust models presented in this paper are quite generic and allow us to obtain the delay component induced only by the security associations along a path. Numerical results obtained by simulations also confirm the accuracy of the analysis. In particular, we can observe from both simulation's and analysis results that, for large and sparsely connected networks, the delay caused by security associations is very small compared to the total delay of a packet. This also means that parameters like network density and nodes' velocity, rather than any trust model parameter, have more impact on the overall delay.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.9A
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• pp.685-696
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• 2009

The requirements of the NGA are to provide broader bandwidth, higher splitting ratio, and longer reach than those of the current FTTH. In the TDMA PON accounting for large percentage in the total FTTH, the increase in distance between the OLT and the ONU leads to the increase in propagation delay and in packet delay three times more than the propagation delay. It is because a packet arrived in the ONU is handled through bandwidth request, grant, and transmission. To reduce the increased packet delay, the OLT have to reduce the cycle time. However, it will cause increased overhead and reduced link efficiency. In this paper, we investigate several problems in TDMA PON when the subscriber access network extended to 60 or 100 Km reach as a NGA goal and provide a method that determines an optimal cycle time to satisfy QoS for delay sensitive traffics. In particular, we suggest a variable equalized round trip delay method and a variable cycle time method. It is shown that the former reduces the packet delay and the latter increase the link efficiency.

• Journal of the Korean Operations Research and Management Science Society
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• v.30 no.2
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• pp.29-40
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• 2005

In this research, we propose packet scheduling algorithm considering different QoS characteristics of real-time traffic and non-real-time traffic in the next generation wireless communication system serving the multimedia traffic and a new efficient framing method cooperated with this packet scheduler. When the selected traffic classes of the selected users are transmitted, our proposed framing method can increase the number of serviced traffic classes by mixing the many different traffic classes within one frame considering data rate decided by the allocated AMC (Adaptive Modulation and Coding) option. Using this proposed method, the fairness among the traffic classes can be achieved and the system performance for total throughput and delay can be enhanced. Simulations are performed to analyze the performance of the proposed framing method. Our proposed packet scheduler and framing method will be applied to the next generation multimedia wireless communication system serving many traffic classes.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.201-208
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• 2010

Mobile Ad Hoc Network(MANET) has highly dynamic topology, hence presents a great challenge on the network performance evaluation and network protocol design. We proposed total path break up time, $\sum_{i}T_i$, as a metric to measure the performance of the total system as well as an individual connection. In this paper, we evaluate and analyze the performance of three mobility models(Random Waypoint, Manhattan, Blocked Manhattan) by applying the total path break up metric, investigate why network parameters such as packet delivery ratio, end-to-end delay, etc. vary by mobility models. We also present analysis result how much AODV Buffer improve packet delivery ratio and increase the end-to-end delay in spite of the path break up.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.10
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• pp.17-28
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• 2008

Rapid transmission of packets is important in mobile ad hoc networks. Therefore, a flooding algorithm which can guarantee a short delay is useful in various ways of packet transmission. Flooding algorithm is one of the packet transmission methods that broadcasts a packet to all nodes within a transmission range. It does not rebroadcast the same packet which is already received from other nodes. Basically, flooding algorithm's advantages are that it simply writes an address and a sequence number in a packet, and it can be adapted for topological changes easily. However, the basic flooding algorithm has a shortcoming that causes excessive traffic because all nodes transmit a packet at least once. To solve this problem, research about flooding algorithms that constrains duplicated transmission of packets based on probabilistic and geographical information is going on. However, the existing algorithm cannot guarantee short delay and low traffic. To reduce a delay, in this paper we propose a flooding scheme where a node which receives a broadcasted packet chooses and allocates a priority to one of its neighbor nodes and then the node transmits the packet promptly to the node to whom the priority was given. Moreover, we propose a totally fresh a roach to constrain duplicated transmission by searching a node that already received the same packet by using node's geographical position information. Lastly, we compare the performance of the proposed algorithm with the existing algorithm through simulation. The results show that the proposed algorithm can distribute packets through a lower number of total packet transmissions and faster delivery time than the existing algorithm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.2
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• pp.289-295
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• 2000

Traffic analysis during past years used the Poisson distribution or Markov model, assuming an exponential distribution of packet queue arrival. Recent studies, however, have shown aperiodic and burst characteristics of network traffics. Such characteristics of data traffic enable the scalability of network, QoS, optimized design, when we analyze new traffic model having a self-similar characteristic. This paper analyzes the self-similar characteristics of a small-scale mixed traffic in a network simulation, the real WAN delay time, TCP packet size, and the total network usage.

• ETRI Journal
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• v.22 no.4
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• pp.40-50
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• 2000

We apply a "sliding-window" Maximum Likelihood(ML) estimator to estimate traffic parameters On-Off source and develop a method for estimating stochastic predicted individual cell arrival rates. Based on these results, we propose a simple Connection Admission Control(CAC)scheme for delay sensitive services in broadband onboard packet switching satellite systems. The algorithms are motivated by the limited onboard satellite buffer, the large propagation delay, and low computational capabilities inherent in satellite communication systems. We develop an algorithm using the predicted individual cell loss ratio instead of using steady state cell loss ratios. We demonstrate the CAC benefits of this approach over using steady state cell loss ratios as well as predicted total cell loss ratios. We also derive the predictive saturation probability and the predictive cell loss ratio and use them to control the total number of connections. Predictive congestion control mechanisms allow a satellite network to operate in the optimum region of low delay and high throughput. This is different from the traditional reactive congestion control mechanism that allows the network to recover from the congested state. Numerical and simulation results obtained suggest that the proposed predictive scheme is a promising approach for real time CAC.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.4
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• pp.8-12
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• 2009

We propose BMPA(balanced multimedia packet allocation) scheme. This scheme considers the issue of optimal sub-carrier allocation in OFDMA multicast system. When RT(real time) packets and NRT(non-real time) packets arrive at the same time, BMPA scheme gives higher weight to RT packets than NRT packets and then, it allocates sub-carriers according to the total weight sum of packets in each user. This process acts as both packet scheduler and sub-carrier allocation. Therefore, each user receives multimedia packets with reliability. With simulation results, it shows that BMPA scheme ensures long-term system throughput and, in average RT packet delay, BMPA scheme greatly outperforms multi-user water-filling algorithm.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.17-18
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• 2007

Mobile WiMAX technology is the key solution for providing high speed internet services at anytime and anywhere in mobile environments as 3.5th wireless technology between 3rd generation and 4th generation wireless technology, and the service demands shall be rapidly increased in future some years. This paper analyzed the QoS performance of Mobile WiMAX technology recommended by IEEE 802.16e specification under the restricted simulation conditions and environments. The major metrics for analyzing QoS performance of Mobile WiMAX are 1) total packet drop rates; 2) transmission / receive packet sizes; 3) end to end delay in node 2; 4) packet drop rate by mobile terminal mobility.