Zbigniew Dziong

Congestion probabilities in a circuit-switched integrated services network

Abstract We derive recurrence relations enabling the direct calculation of the joint distribution of the number of busy channels in a circuit-switched network whose offered traffic streams require a variable number of channels on each link. Approximate congestion probability calculation methods are developed based on the estimation of marginal link occupancy distributions taking account of link traffic correlation. These approximations are tested on a number of simple two-link examples.

A framework for bandwidth management in ATM networks—aggregate equivalent bandwidth estimation approach

A unified framework for traffic control and bandwidth management in ATM networks is proposed. It bridges algorithms for real-time and data services. The central concept of this framework is adaptive connection admission. It employs an estimation of the aggregate equivalent bandwidth required by connections carried in each output port of the ATM switches. The estimation process takes into account both the traffic source declarations and the connection superposition process measurements in the switch output ports. This is done in an optimization framework based on a linear Kalman filter. To provide a required quality of service guarantee, bandwidth is reserved for possible estimation error. The algorithm is robust and copes very well with unpredicted changes in source parameters, thereby resulting in high bandwidth utilization while providing the required quality of service. The proposed approach can also take into account the influence of the source policing mechanism. The tradeoff between strict and relaxed source policing is discussed.

Adaptive traffic admission for integrated services in CDMA wireless-access networks

Code-division multiple-access (CDMA) is a serious candidate for personal communication systems at 1.9 GHz in North America. We consider the issue of bandwidth management in a CDMA integrated wireless-access network with heterogeneous services. A framework for adaptive connection admission in the up-link direction is proposed. It is based on estimation of the interference at the base station receivers. The estimation algorithm employs a linear Kalman filter which is driven by a measurement of the interference and by predicted traffic parameters of the admitted connections. We derived several generic variants of the control architecture for the up-link direction to assess the main characteristics of the framework and to determine the trade-offs between complexity and performance. They vary from a fixed strategy with fixed power control to an adaptive strategy with full information about network state and adaptive power control. A numerical study of the proposed framework shows that the estimated value of the average interference adapts well to the real value under nonstationary and nonuniform environment. This feature results in high network utilization for arbitrary traffic conditions.

Fair-efficient call admission control policies for broadband networks—a game theoretic framework

A fundamental problem in connection oriented multiservice networks (ATM and STM) is finding the optimal policy for call acceptance. One seeks an admission control policy that efficiently utilizes network resources while at the same time being fair to the various call classes being supported. The theory of cooperative games provides a natural and precise framework for formulating such multicriterion problems as well as solution concepts. The authors describe how this framework can be used for analysis and synthesis of call admission strategies in broadband networks. In particular they investigate the Nash (1950), Raiffa-Kalai-Smorodinsky (Raiffa, 1953; Kalai and Smorodinsky, 1975), and modified Thomson (Cao, 1982) arbitration solutions from game theory. The performance of all solutions is evaluated by applying the value iteration algorithm from Markov decision theory. The approach is illustrated on a one-link network example for which the exact solutions can be achieved. The results indicate that the arbitration schemes from game theory provide some attractive features especially when compared to traditional control objectives: blocking equalization and traffic maximization. The authors also compare the optimal solutions with some simplified policies belonging to four different classes: complete sharing, coordinate convex, trunk reservation, and dynamic trunk reservation. The comparison indicates that in many cases, the trunk reservation and dynamic trunk reservation policies can provide fair, efficient solutions, close to the optimal ones.

Admission control and routing in ATM networks

Abstract Different approaches for effective bandwidth allocation in an ATM link are investigated. The results can be useful in constructing some simple admission models. A framework for flow control and routing in ATM networks is proposed. It is based on methods developed for circuit-switched networks.

An analysis of near optimal call admission and routing model for multi-service loss networks

A state-dependent call admission and routing policy for a multiservice circuit-switched network is analyzed. The policy is based on decomposition of the Markov decision problem into a set of separable link problems. To provide an exact link analysis model a value iteration algorithm was offered. This allows examination of the accuracy of several approximations used to reduce the complexity of the problem. The numeral study showed that the convergence of the analyzed strategy is achieved in at most two iterations. The study also showed the good traffic efficiency of the approach and confirmed the predicted ability to control the distribution of call classes grade of service. The approach, together with its sensitivity analysis with respect to the arrival rates, provides a very general framework for studying, constructing, and optimizing other call admission and routing strategies. The results of sensitivity analysis are used to compare the proposed decomposition approach with the decomposition approach developed by F.P. Kelly (1988) for optimization of a load sharing policy. Also, the relationship to other routing strategies based on Markov decision theory is investigated.<<ETX>>

Multiuser detection based MAC design for Ad Hoc networks

Recent technological advances in code division multiple access (CDMA) with multiuser detection (MUD) allow to consider this technology for future wireless Ad Hoc networks. Due to the fundamentally different physical layer architecture, application of MUD in Ad Hoc networks requires novel approaches for medium access control (MAC) and scheduling mechanisms in order to take advantage of the new features. This paper proposes a new MAC and scheduling paradigm which addresses three design issues: distributed dynamic code assignment that avoids code collision, distributed scheduling scheme that provides fairness among contending nodes, and organization of the data transmission based on multiuser detection. Simulation model is used to verify the performance gains from the increased spectrum reuse due to multiuser reception and from the reduced interference due to multiuser detection. This is done by comparisons with existing MAC paradigms, such as CSMA/CA and parallel CDMA.

Virtual network concept and its applications for resource management in ATM based networks

In the paper we describe a framework for resource management and traffic control which is based on the virtual network concept. In this context the virtual networks are used as a toot for customization of networks management functions and for virtual separation of network resources. We identify three main categories of virtual network applications (service, user and management oriented virtual networks). We discuss generic and application oriented problems, which have to be solved to take full advantage of the proposed framework. We also study the relation between the virtual network concept and the virtual path concept in the context of bandwidth management. The study indicates that using virtual paths for bandwidth management involves some inherent contradictions.

Control of multi-service loss networks

A state-dependent routing policy for a multi-service circuit-switched network is synthesized. To meet different requirements, the objective function is defined as the mean value of reward from the network. The theory of Markov decision processes is applied to find the optimal routing policy. It is shown that under the link independence assumption the problem can be decomposed into a set of link analysis problems. In this approach the optimal decision is a function of state-dependent link shadow prices, which are interpreted as prices for using each link from the path. The approach is implementable even for large systems if certain approximations are used. It is shown that the proposed model provides good traffic efficiency and automatic flow control, and that by means of the call reward parameters one can almost independently control the grade of service of each call class.<<ETX>>

Resource allocation in macrocell-femtocell network using genetic algorithm

In this paper, we consider the problem of resource allocation in two-tier networks taking into consideration nondense femtocell deployments. The following limitations can be remarked from the prior work in the field of resource allocation: (1) resources are underutilized due to the equal power distribution in macrocell, (2) access to public users in femtocells is restricted to avoid depriving own subscribers transmissions, and (3) degradation of signal-to-noise ratio due to noise effects has not been evaluated. To overcome these limitations, we propose a joint power and bandwidth allocation among two tiers together with base station selection using genetic algorithm. Our solution is able to: (1) maximize the overall system throughput, (2) find an appropriate serving base station for each user, and (3) bandwidth and power assigned to each user. Simulations were conducted and a comparison with a Weighted Water Filling algorithm is carried out.