Kenta Yasukawa

Distributed Delay Estimation and Call Admission Control in IEEE 802.11 WLANs

In recent years VoIP and IEEE 802.11 networks have seen a rapid growth. In IEEE 802.11 networks, an Access Point (AP) and the stations (STAs) it serves form a Basic Service Set (BSS). Each AP can support a limited number of concurrent voice calls; we refer to this number as the AP capacity. After the number of concurrent voice calls in the BSS surpasses the AP capacity, the communication of all users at that AP suffers from high delay, and therefore, poor quality. These are the problems we address with Call Admission Control (CAC). We propose a mobile-station-based CAC mechanism. One of the strengths of the proposed approach is that it is very simple and yet accurate, while not requiring any probing of the medium. Our approach is entirely client-based, thus not requiring any changes in the infrastructure and the protocol.

Proposal of multipath routing method focusing on reducing delay jitter

A new approach to reducing delay jitter that uses multipath routing and redundant packets is described. Delay jitter causes data loss at the application layer and prevents the smooth provision of real-time multimedia communication services. In this paper, a policy of multipath routing for reducing delay jitter is discussed and an algorithm is proposed that solve the problem of selecting two paths for reducing delay jitter. The algorithm outputs a set of paths that satisfy a specified delay constraint; they share a few nodes and have a small delay difference. Simulation results showed that the set of paths is more suitable for reducing delay jitter than those selected using the routing method of a path diversity scheme.

Classification of nonstream flows to reduce negative interactions between stream and nonstream flows

In this paper, we term multimedia streaming application traffic stream flows, and the other usual application traffic nonstream flows. There are many problems where both flows are aggregated on a shared link, because different TCP and UDP behaviors cause negative interactions. To solve these, we propose a new method that reduces these interactions. In this paper, we classify nonstream flows into several classes based on assumptions that the traffic patterns of nonstream flows vary depending on upper-layer-applications and they have different interactions with stream flows. First, we discuss our classification of nonstream flows. Second, we reveal the characteristics of nonstream flows in each class. We then evaluate our method using a principle algorithm, and present the outstanding effective results we obtained through simulation experiments.

Nearly Equal Delay Path Set Configuration (NEED-PC) for Multipath Delay Jitter Reduction

Delay jitter degrades the quality of delay-sensitive live media streaming. We investigate the use of multipath transmission with two paths to reduce delay jitter and, in this paper, propose a nearly equal delay path set configuration (NEED-PC) scheme that further improves the performance of the multipath delay jitter reduction method for delay-sensitive live media streaming. The NEED-PC scheme configures a pair of a maximally node-disjoint paths that have nearly equal path delays and satisfy a given delay constraint. The results of our simulation experiments show that path sets configured by the NEED-PC scheme exhibit better delay jitter reduction characteristics than a conventional scheme that chooses the shortest path as the primary path. We evaluate the performance of path sets configured by the NEED-PC scheme and find that the NEED-PC scheme reduces delay jitter when it is applied to a multipath delay jitter reduction method. We also investigate the trade-off between reduced delay jitter and the increased traffic load incurred by applying multipath transmission to more flows. The results show that the NEED-PC scheme is practically effective even if the amount of additional redundant traffic caused by using multipath transmission is taken into account.

Tentative Accommodating and Congestion Confirming Strategy--A Novel Admission Control Strategy for Packet Switching Networks--

Admission control is becoming an essential technique for IP networks to provide full-fledged multimedia streaming services. Although signaling-based schemes are utilized to achieve this, these are difficult to deploy and can hardly achieve strict admission control taking the properties of packet arrival into consideration. In this paper, we propose a novel admission control strategy called the Tentative Accommodating and Congestion Confirming Strategy (TACCS). The main idea is to accommodate incoming flows tentatively and confirm congestion after a certain period. Since tentative accommodating enables us to generate the same situation as where incoming flows have been accommodated, TACCS makes it possible to control admission considering the properties of packet arrival after they have been accommodated, without collecting resource information in advance. From the results of mathematical analysis, we confirmed that TACCS enabled a domain to control admission without a centralized management agent and we provided guidelines for configuring parameters of TACCS.

Concept of admission control in packet switching networks based on tentative accommodation of incoming flows

We propose a novel admission control strategy called the Tentative Accommodating and Congestion Confirming Strategy (TACCS). The main idea is to accommodate incoming flows tentatively and confirm congestion after a certain period. TACCS makes it possible to control admission without collecting resources information in advance. Our simulation results demonstrated that TACCS enabled a domain to control admission without a centralized management agent.

Edge-Based TACCS: A More Scalable TACCS Based on Cooperation of High Functional Edge Nodes

Various multimedia streaming have started to be offered in Internet protocol (IP) networks. However, since current networks cannot operate well if the consumers end system sends multimedia stream at will, an admission control is becoming an important part of IP networks. Therefore, we previously proposed an admission control scheme we call tentative accommodating and congestion confirming strategy (TACCS). The basic idea is to accommodate incoming flows tentatively and then confirm congestion after a certain period. In TACCS, the ingress nodes of a domain make flow-accommodating decisions based on information about packet-loss events. The information is assumed to be advertised from congestion detection agents (CDAs) located in the domain. If comparable performance could be achieved without adding CDA functions to core nodes, the cost of deploying TACCS would be reduced and its scalability would be improved. We have thus developed an enhanced TACCS called edge-based TACCS that achieves admission control based on cooperation of high functional edge nodes and does not depend on CDAs in the core network. Simulation showed that the performance of edge-based TACCS is comparable to that of conventional TACCS that depends on CDAs in the core network.

Analysis of tentative accommodating and congestion confirming strategy: a novel admission control strategy for packet switching networks

We previously introduced a concept for admission control in packet switching networks that makes deploying a centralized management agent and collecting resource information in advance unnecessary. The new concept is to tentatively accommodate incoming flows and decide whether or not they can be accommodated after an observation period. We called the admission control scheme based on this concept as tentative accommodating and congestion confirming strategy (TACCS). We have now modeled a TACCS system by combining M/sup X/ /M/c/c loss and M/G/1/K queuing systems and mathematically analyzed its performance and characteristics. The analytical results showed that TACCS enables a domain to control admission without using a signalling scheme or a centralized management agent. We have also provided guidelines for configuring the values of parameters for TACCS.

Theoretical Analysis of Difference Between Edge-Based and Core-Node-Supported TACCS

Internet protocol (IP) networks need admission control mechanism to provide full-fledged multimedia services. Therefore we previously proposed an admission control scheme called the tentative accommodating and congestion confirming strategy (TACCS). The basic idea of TACCS is to tentatively accommodate incoming flows and then, after a certain period, determine whether accommodating them has created congestion. In this scheme, the ingress nodes of a domain make flow- accommodation decisions based on packet-loss event information. The information is assumed to be advertised from congestion detection agents (CDAs) located in the domain. However, adding CDA functionality to core nodes is a barrier to deploy TACCS and limits its scalability. Thus, we furthermore developed an enhanced version called edge-based TACCS that performs admission control on the basis of only cooperation between edge nodes- it does not depend on CDAs in the core network. In this paper, we compared the operation of the edge-based version with that of the core-node-supported TACCS and investigated a problem: some flows, which should be rejected in the core- node-supported version, could be wrongly accommodated in the edge-based TACCS. Theoretical analysis of this rejection failure problem showed that it does not significantly degrade flow quality, meaning that edge-based TACCS is feasible.

Class assigning management for stream flows considering characteristics of nonstream flow classes

We term multimedia streaming application traffic stream flows, and the other usual application traffic nonstream flows. There are many problems where both flows are aggregated on a shared link, because different TCP and UDP behaviors cause negative interactions. One way to solve these problems is to isolate stream and nonstream flows to different classes. However, because it is then difficult to determine the bandwidth allocation for each class, it is hard to implement on large scale networks. We therefore propose a dynamic class assignment method that maintains the QoS and that has a higher scalability than dynamic bandwidth allocation schemes. It is workable on Diffserv AF PHB, and is outlined as follow. We classify nonstream flows into four classes and dynamically assign stream flows to the classes, taking the conditions and characteristics of the classes into consideration. We propose an algorithm for our dynamic class assignment method and provide some simulation results where it could provide constant qualities with stream and nonstream flows, adapting to changing traffic.