Katsunori Yamaoka

Transparent Unicast Translation to Improve Quality of Multicast over Wireless LAN

Media broadcasting services using Internet protocol (IP) multicast are emerging and IEEE 802.11 wirelEss LAN (WLAN) has been widely deployed. Therefore, the opportunities to receive multicast streaming over WLAN are expected to grow. However, because of restrictions on the IEEE 802.11 standard, the transmission rate and the reliability of multicast over WLAN are lower than those of unicast. In this paper, we propose a transparent multicast / unicast translation method which translates a multicast packet into multiple unicast packets at the media access control (MAC) layer, so that we can utilize the higher transmission rates and retransmission function that are only available with unicast. Our theoretical analysis and experiment show that the proposed method improves the efficiency and reliability of multicast over WLAN.

Maximum-Bandwidth ALM Tree on Tree Network

It is important to use an ALM (application layer multicast) tree with broad bandwidth to ensure the quality of streaming applications. However, when constructing an ALM tree without information on underlay traffic, we cannot know how much congestion there is in links. Therefore, if unexpected congestion in links occurs, the quality of ALM transmissions may worsen. However, no polynomial-time algorithms for constructing maximum-bandwidth ALM trees with information on underlay traffic exist. n nWe regarded an underlay network as a tree network topology in our previous work, and presented a polynomial-time algorithm that was used to construct a maximum-bandwidth ALM tree. We also proved that we could obtain an optimal ALM tree. However, we had not yet evaluated our algorithm by simulation. n nHere, we discuss our evaluation of the algorithm we propose and a conventional one. We found our algorithm could achieve a broader bandwidth ALM tree at lower computational cost, especially in large networks.

Accepting more general telephone calls in emergency situations by limiting general call holding time under trunk reservation control

We investigated the effect of limiting the holding time of general telephone calls on their acceptance rate during an emergency situation. Simulation using a queuing system model of a telephone exchange showed that limiting the holding time of general calls increased the number of accepted general calls even when their acceptance was threshold-controlled while still enabling the required number of emergency calls to be accepted. An investigation of the relationship between the traffic intensity of accepted general calls and the general call-blocking rate showed that an upper limit on the traffic intensity can be set by using threshold control. Limiting the holding time enables more general callers to share the acceptable traffic intensity, which reduces the general call-blocking rate. Calculation of the call-blocking rate for various numbers of lines in a telephone exchange showed that the effect of a general call holding time limitation on the general call-blocking rate is equivalent to that obtained by adding a certain number of lines.

Optimal threshold characteristics of call admission control by considering cooperative behavior of users (loss model)

Call admission control (CAC) is an important technology for maintaining Quality of Service (QoS) in Software-Defined Networking (SDN). The most popular type of CACs is trunk reservation (TR) control, and many TR control methods had been proposed for improving evaluation values such as call blocking probability or the resource utilization rate. In general, some users under these TR control methods may behave cooperatively. However, conventional TR methods do not take into account a users cooperative behavior when they begin to communicate. In this paper, we propose a novel TR-type CAC method by considering the cooperative behavior of some users. This proposed method is presented using the loss model of queueing theory for the call-level analysis of a single link. We also analyze the characteristics of the optimal control parameter.

Proof of optimal algorithm for maximum-bandwidth ALM tree construction

We construct an ALM (application layer multicast) tree that achieves the maximum bandwidth by using underlay traffic information. Since this problem was previously shown to be NP-hard, no polynomial-time algorithms for maximum-bandwidth ALM tree construction exist. In our work, we assume that the underlay network has a tree network topology, and we show a polynomial-time algorithm that constructs a maximum-bandwidth ALM tree on such a tree network topology. We propose an ALM tree construction algorithm that achieves bandwidth b and apply this algorithm with various bandwidth values b. We show that it can make a maximum-bandwidth ALM tree in polynomial time.

An access-point selection algorithm for user QoS and system optimization based on user cooperative moving

We propose an optimal access-point (AP) selection algorithm for maximizing system throughput while preserving newly arrived-user throughput. In our algorithm, newly arrived users cooperate with a wireless area network system they are trying to use, i.e., they are willing to move toward an appropriate AP. We use our algorithm to determine the optimal AP. Moreover, we discuss the effectiveness of our proposed algorithm by using numerical analysis.

A basic study of the flow admission control of mixed loss and delay system based on equality of heterogeneous traffic

We have proposed a novel Call Admission Control (CAC) to maximize total user satisfaction in a heterogeneous traffic network and showed the effectiveness of our CAC by using optimal-threshold from numerical analysis[1]. In our previous CAC, when a new broadband flow arrived and if total accommodated bandwidth was more than or equal to the threshold, the arriving new broadband flow was rejected. In actual networks, however, users may accept to wait for a certain period until the broadband flow, such as video, begins to play. In this paper, when total accommodated bandwidth was more than or equal to the threshold, arriving broadband flows wait instead being rejected. As a result, we can greatly improve total user satisfaction.

A Basic Study of Heterogeneous Flow Admission Control Based on Equality of Flow Classes

We propose a novel flow admission control that minimizes the total call-blocking rate by treating heterogeneous flows equally. We focused on the static-state bandwidth load, which refers to how much bandwidth is used statically by a smaller class of flow than a newly arriving flow. In this paper, we analyze the characteristics of different types of loads, explain the development of a call-blocking curve to minimize the total call-blocking rate, and demonstrate good performance by this call-blocking curve.

A Threshold Configuration for Flow-Admission Control Based on the Equality (Two-Type Flow Model)

We have developed a novel call admission control (CAC) to minimize the total call-blocking rate on the basis of a new philosophy in which heterogeneous traffic is treated equally in network. We also obtained optimal threshold that minimizes the total call-blocking rate [1]. However, to obtain this optimal threshold, we needed to full-search all threshold candidates. In this paper, we propose an approximation formula to obtain suboptimal threshold based on theoretical characteristic analysis and demonstrate that this approximation formula performs well.

Relationship between packet loss probability and burst parameters for two types of traffic

A call admission control (CAC) method based on the equality of two types of traffic has been proposed for minimizing the total call-blocking rate. However, application of this CAC method to a packet switched network may increase packet loss because packets have bursty characteristics. The length of time in which bursty arrivals continue is called the talk spurt in ON-OFF modeling of the packet arrival process. When the talk spurt is short, the number of arriving packets per unit time (the burst density) increases under the assumption in ON-OFF model that the average bandwidths of the flows are fixed. This can cause packet losses. Therefore, the relationship between the packet loss probability and the talk spurt must be analyzed because burst density affects packet loss probability. However, the characteristics of the packet loss probability when the talk spurt changes for two types of traffic need to be clarified. In this paper, we link the CAC parameters with the burst parameters for two types of traffic, narrowband flows and broadband flows, in which the bursty traffic follows the Markov-modulated Poisson process (MMPP). Furthermore, we numerically analyze the characteristics of the packet loss probability for a given number of flows using queueing theory. The results quantitatively show that the packet loss probability is substantially higher when the burst density is higher. They also show that the packet loss probability is drastically affected by the burst density of broadband flows because their bandwidth is wider.