(A) study on traffic control schemes for guaranteed QoS in ATM networks

Abstract

The main objective of this dissertation is to analyze several problems in asynchronous transfer mode (ATM) networks and to propose traffic control schemes for solving the problems. Although a general framework for traffic control and congestion control in ATM networks is defined, there are many problems to be solved for each service class and heterogeneous services. One problem is that when the policing function is used together with a cell loss priority control scheme for all service classes, a measurement phasing problem can occur in usage parameter control/network parameter control (UPC/NPC) functions. The measurement phasing problem makes it difficult to define and commit cell loss ratios for guaranteed quality of service (QoS). Another problem is related with the cell delay variation tolerance that should be exactly specified at traffic contract for a UPC/NPC to guarantee QoS, but after passing multiplexers the cell interarrival pattern becomes a random variable. Thus, the multiplexing operation makes the determination of the cell delay variation tolerance difficult. The other problem is in the connection admission control (CAC) function for variable bit rate (VBR) traffic. By the statistical characteristics of VBR traffic, the equivalent bandwidth for a VBR connection is difficult to determine. Finally, when the ATM network is extended to air interface, some method for medium access control (MAC) of the shared channel is necessary. The access control needs to provide a fair and efficient method for non-real-time traffic and to reserve a bandwidth for real-time isochronous traffic for guaranteed QoS in the face of an unreliable channel. In this dissertation, we first study the cause of measurement phasing problem in the UPC/NPC function. To sove the problem, we propose a new UPC/NPC algorithm. By using the UPC/NPC algorithm, we can define the cell loss ratios for CLP=0 and CLP=0+1 cell streams without the measurement phasing problem under any conditions. ...