David W. Petr

Quality of service scheduling in cable and broadband wireless access systems

Several last mile high-speed technologies have been explored to provide Internet access and multimedia services to end users. Most notable of those technologies are hybrid fiber coax (HFC) cable networks, digital subscriber line (DSL), satellite access, and fixed broadband wireless access (BWA) systems. The de facto standard for delivering broadband services over HFC networks is the Data Over Cable Service Interface Specifications (DOCSIS) protocol. For BWA systems, on the other hand, a new protocol, called IEEE 802.16, was developed for the same purpose. This paper presents a new and efficient scheduling architecture to support bandwidth and delay quality of service (QoS) guarantees for both DOCSIS and IEEE 802.16. Our design goals are simplicity and optimum network performance. The architecture we develop supports various types of traffic including constant bit rate, variable bit rate (real-time and non-realtime) and best effort.

Priority discarding of speech in integrated packet networks

The authors discuss the control of short-term congestion, which is referred to as overload, in integrated packet networks (IPNs) containing a mix of data, speech, and possibly other types of signals. A system model is proposed that assigns a delivery priority to each packet (speech or otherwise) at the transmitter and discards speech packets according to delivery priority at any point in the network in response to overload. This model attempts to minimize per-packet processing at networks nodes. The research described is guided by two principles for IPN design: minimal per-packet processing and flexibility due to signal structure. The quality of the received speech is maintained by classifying speech segments according to their structure and coding them in a way that ensures ease of lost-packet regeneration at the receiver. The results of an experiment are reported that confirmed the general validity of this model from the standpoint of transmitter and receiver processing and subjective quality. >

Nested threshold cell discarding for ATM overload control: optimization under cell loss constraints

Overload control in asynchronous transfer mode (ATM) networks is dealt with via priority cell discarding mechanisms governed by a set of nested queue fill thresholds. An efficient search technique is developed which is applicable to any number of discarding priorities for determining the set of thresholds that optimize the offered load when constraints on cell loss (discarding) probabilities are specified. Results are presented as a function of queue capacity for given traffic distribution and arrival statistics. The results indicate that nested threshold discarding systems can support significantly higher traffic loads than systems without priorities. The sensitivity of the performance advantage to traffic mix and cell loss constraints is also illustrated. The efficient search procedure is shown to provide substantial computational gain when there are more than two discarding priorities.<<ETX>>

A predictive self-tuning fuzzy-logic feedback rate controller

This paper addresses the design and analysis of an end-to-end rate-based feedback flow control algorithm motivated by the available bit rate (ABR) service in wide-area asynchronous transfer mode (ATM) networks. Recognizing that the explicit feedback rate at time t will not affect the ABR buffer until time t+D for some D/spl ges/0, our approach is to first predict the ABR buffer status at time t+D, then base fuzzy-logic rate control decisions on these predicted values, and finally tune the controller parameters using gradient descent methods. Simulations show that this predictive self-tuning fuzzy-logic (PSTF) control scheme is efficient, stable, and outperforms other proposed ABR rate controllers in a variety of network environments. With delays corresponding to a US coast-to-coast connection, the PSTF controller can maintain high link utilization, avoid buffer overflows, and provide fair allocation of resources.

Design and analysis of a bandwidth management framework for ATM-based broadband ISDN

When designing and configuring an ATM-based B-ISDN, it remains difficult to guarantee the quality of service (QoS) for different service classes, while still allowing enough statistical sharing of bandwidth so that the network is efficiently utilized. These two goals are often conflicting. Guaranteeing QoS requires traffic isolation, as well as allocation of enough network resources (e.g., buffer space and bandwidth) to each call. However, statistical bandwidth sharing means the network resources should be occupied on demand, leading to less traffic isolation and minimal resource allocation. The authors address this problem by proposing and evaluating a network-wide bandwidth management framework in which an appropriate compromise between the two conflicting goals is achieved. Specifically, the bandwidth management framework consists of a network model and a network-wide bandwidth allocation and sharing strategy. Implementation issues related to the framework are discussed. For real-time applications the authors obtain maximum queuing delay and queue length, which are important in buffer design and VP (virtual path) routing.

Optimal packet discarding: an ATM-oriented analysis model and initial results

A problem associated with overload control by packet discarding in integrated packet networks such as a broadband integrated services digital network (B-ISDN) is considered. The question of optimality in priority packet discarding is examined in order to minimize the service degradation associated with the discarding. An analysis model which is consistent with asynchronous transfer mode (ATM) operation of such a network is presented. It is shown how dynamic programming can be used with this model to find an optimal discarding policy, and initial results of such an analysis for queuing systems with a single buffer position are presented. It is shown by example that the optimal policy can perform significantly better over a wide range of parameter values than the default policy of discarding arriving packets only when the queue is full.<<ETX>>

Using optimization to achieve efficient quality of service in voice over IP networks

For Internet telephony to be a viable alternative to the public switch telephone network (PSTN), efficient and high quality communications are required. This paper proposes an optimization algorithm that selects parameters like the coding scheme, packet loss bound, and maximum link utilization level in a voice over IP (VoIP) network The goal is to deliver guaranteed quality of service (for voice) while maximizing the number of users served. A VoIP architecture is also discussed that could use optimization algorithms to dynamically provision VoIP networks.

Self-tuning fuzzy traffic rate control for ATM networks

This paper addresses the problem of rate control for the available bit rate (ABR) service class in an ATM network. A Sugenos method based fuzzy ABR rate controller is proposed in this center. This fuzzy congestion control approach is optimized by a conventional gradient search method, in which the parameters of the output fuzzy functions are adapted based on the gradient of a certain control criterion. By simulation using real trace data we show that ATM networks can approach the desired output behavior very effectively and also maintain high utilization of the network through the proposed self-tuning fuzzy congestion control scheme. Low cell loss ratio and high link utilization are achieved.

A class-oriented replacement technique for lost speech packets

A replacement technique for lost speech packets is presented. This technique is based on the classification of the packets into four distinct classes: background noise, voiced speech, fricatives, and other. Different encoding schemes and lost packet replacement techniques are used for each class. Results of subjective tests indicate that giving preferential delivery treatment to packets based on class can be used to improve subjective quality. The replacement strategy renders the reconstructed signal indistinguishable from the original utterance for packet loss rates up to 47% for background noise packets, 8% for fricative packets, and 4% for other packets. For voiced packets, the replacement is distinguishable from the original signal even for packet loss rates lower than 5%, but significant improvement may be possible by reducing the memory associated with the voiced speech coding process.<<ETX>>

A survey of pricing for integrated service networks

Advances in technology have greatly increased the demand for a single integrated service network that can provide multiple service classes for different user requirements. For such a multiple-service network, congestion control is one of the key issues to be addressed. However, without an appropriate mechanism to encourage end users to use the network properly, over-utilization and congestion are unavoidable. For this problem, it is widely accepted that pricing is a proper tool to manage congestion, encourage network growth, and allocate resource to users in a fair manner. However, how to charge for the traffic and at what price is still under study. In this paper, we first briefly review the state of the art and technological growth of congestion control for integrated service networks (ISN). Subsequently, we present a summary of the recent developments on various pricing policies and different charging and billing schemes that have been proposed for ATM and Internet Differentiated Services. Some architecture and implementation issues are also discussed. Finally, some future trends are identified.