Showing papers in "International Journal of Communication Systems in 1997"

Feedback control of congestion in packet switching networks: the case of multiple congested nodes

Abstract: In this paper, an analytical method for the design of a congestion control scheme in packet switching networks is presented. This scheme is particularly suitable for implementation in ATM switches, for the support of the available bit rate (ABR) service in ATM networks. The control architecture is rate-based with a local feedback controller associated with each switching node. The controller itself is a generalization of the standard proportional-plus-derivative controller, with the difference that extra higher-order derivative terms are involved to accommodate the delay present in high-speed networks. It is shown that, under the specific service discipline introduced here, there exists a set of control gains that result in asymptotic stability of the linearized network model. A method for calculating these gains is given. In addition, it is shown that the resulting steady state rate allocation possesses the so-called max-min fairness property. The theoretical results are illustrated by a simulation example, where it is shown that the controller designed, using the methods developed here, works well for both the service discipline introduced in this paper and for the standard FCFS scheme. © 1997 John Wiley & Sons, Ltd.

Performance of cell loss priority management schemes in a single server queue

Abstract: The throughput optimality of priority management strategies in a single buffer has been studied for a general aggregate arrival law. The tight upper bounds found are useful to understand optimality in the utilization of specific priority schemes such as push-out buffer (POB) and partial buffer sharing (PBS). This paper further focuses on the maximum allowable load ρmax versus the priority mix α for a PBS and a random push-out buffer (RPOB) of size K for a wide variety of arrival processes. The role of priorities in a special type of bursty arrivals, the compound Poisson process with constant burst length and random priority assignment within the burst is found to be less pronounced than that of ‘pure’ Poisson arrivals. On the other hand, the results for ON–OFF cell arrivals modelled by a MMPP(2), MMPP(3), and higher order Markov modulated processes (MMP) closely follow the behaviour of the maximum allowable load in the RPOB with Poisson arrivals, however, scaled to lower loads. The results indicate that the priority mix distribution within the aggregate arrival flow influences the shape of ρmax(α)-curve more than the aggregate arrival distribution itself. © 1997 John Wiley & Sons, Ltd.

Integrated dynamic distributed routing and admission control in ATM networks

Abstract: A node-by-node admission control and routing scheme for ATM networks is devised. The scheme is based on the subdivision of traffic into a number of classes, characterized by different performance requirements. At each network node, for all outgoing links, link capacity partitions are periodically assigned to the traffic classes, as the result of an optimization problem over a fixed time interval. Local access control rules compute the maximum number of connections of each class that a link can accept within the assigned capacity. Incoming call connection requests are forwarded in a hop-by-hop fashion. Each node traversed, first checks the presence of resources needed to accept a new connection and guarantee all quality of service (QoS) requirements. This is done by using the local access control rule. Then, it chooses the next node along the path on the basis of a distributed routing strategy. This minimizes a cost function accounting for local instantaneous information, as well as for aggregate information that is passed periodically among adjacent nodes. Two routing strategies are introduced. In the first scheme, a new call is rejected if, at a certain node along the path, there are not enough resources to guarantee QoS requirements, and no recovery mechanism is implemented. In the second scheme, an alternative path is looked for after the first failure. Simulation results are presented which show a comparison between the two proposed routing strategies. Comparison is also made between the proposed scheme and the other approaches. © 1997 John Wiley & Sons, Ltd.

Distributed traffic adaptive channel allocation

Abstract: Dynamic channel allocation (DCA) schemes adapt to the time variant demand for channels in cellular mobile telephony systems. In this paper we propose a DCA scheme that smoothly changes the channel allocation by solving the following problem. Given a cell structure, a collection of channels, the frequency reuse distance, an allocation of channels to cells, and the number of active connections per cell, accommodate a new call or a new handover by minimally reconfiguring the established allocation of channels to cells. First, this problem is formulated as 0–1 quadratic programming problem. Next, we present a distributed, heuristic solution to the problem, which is based on the observed behaviour of the optimal algorithm. Finally, we present some simulation results on the performance and the feasibility of the distributed algorithm. © 1997 John Wiley & Sons, Ltd.

Analysis of packet loss in transport layer over ATM networks

Abstract: In ATM networks, when cells are lost due to congestion, packets containing the lost cells should be retransmitted in the transport layer, which manages the end-to-end communication. The probability that a packet contains at least one lost cell depends on the packet length. It is thus very likely that the performance of the end-to-end communication is influenced by the packet length. In this paper, we analyze the packet loss probability and the maximum achievable throughput when a block of data is divided into packets of fixed size and the lost packets are retransmitted based on the selective repeat ARQ. Through the analysis, we examine the effect of the packet length and the peak cell transmission rate on the performance measures.

Power control supported dynamic channel assignment in cellular radio systems

Abstract: Transmitter power control is an effective technique to reduce co-channel interference and increase system capacity for cellular radio networks. Dynamic channel assignment can also be used to improve spectrum efficiency and thus increases the system capacity. This paper investigates channel assignment algorithms which combine dynamic channel assignment with signal-to-interference ratio balanced power control and proposes a new algorithm. Simulation results show that this new scheme can greatly reduce the channel reassignment rate and still maintain satisfactory performance. It may thus be used as an effective channel assignment scheme in cellular mobile systems. © 1997 by John Wiley & Sons, Ltd.

Evaluation of a terrain‐based point‐to‐point propagation model in the 900 MHz band

Abstract: The accuracy of a semi-empirical point-to-point propagation model, based on terrain data information close to the receiver, is tested. The evaluation is performed through extended transmission loss measurements taken in an urban environment (Athens region) in the 900 MHz band. The prediction error is calculated for each measurement point and coordinated with detailed terrain information. Specifically, the evaluation of the model is separately performed for various categories of measurement data with respect to the measurement point's effective height and line-of-sight conditions. ©1997 by John Wiley & Sons, Ltd.

Nonlinear dynamics in telecommunication systems: design and implementation of a large array of service processing elements

Abstract: A large flexible array of nonlinear service processing elements, which capture the functional characteristics of the signalling mechanisms of switching nodes in asynchronous heterogeneous networks (e.g. broadband ISDN), has been designed and implemented. The array is based on field programmable gate arrays and allows a wide range of network configurations and conditions to be explored at low cost with different types, numbers and arrangements of processing elements and architectures. The array provides a rapid and flexible way of studying the service dynamics of large arrays of interconnected multi-processor systems, under normal and abnormal service loading conditions. It also allows integration issues, stability criteria and fault tolerance in the co-ordination and control of asynchronous distributed heterogeneous networks to be investigated. Initial studies using the array have confirmed the existence of various behaviours (e.g. chaos, persistent oscillations) seen in real telecommunication systems. © 1997 by John Wiley & Sons, Ltd.

MPEG over ATM DBR service class for high quality transmission and effective bandwidth usage

Abstract: The highly bursty nature of the moving picture experts group (MPEG) determines the bandwidth when it is applied to the asynchronous transfer mode (ATM) deterministic bit rate (DBR) service class. Furthermore, the MPEG source must declare peak cell rate (PCR), one of the traffic descriptors used in the call admission control (CAC) procedure, before actual transmission in ATM networks. However, the real-time encoding of the MPEG video introduces a difficulty in predicting a maximum picture size of the video, which is necessary to determine PCR. When an MPEG source can be equipped with the capability to adjust the encoding rate to the allocated bandwidth, the burstiness of the MPEG video can be lowered and the uncertainty in predicting PCR is avoided to some extent. In this case, a problem is apparently quality degradation caused by introducing such a rate adaptation mechanism, which is the main subject of this study. For the rate adaptation method, we consider a priority control method, a space reduction method, a time reduction method and a bandwidth renegotiation method. Quality of the video is evaluated and compared in terms of signal-to-noise ratio (SNR) as well as mean opinion score (MOS) because users' perception becomes an important measure of the quality of video transmissions. Through experimental results, it is shown that the space reduction method is useful for real-time transmission, whereas the time reduction method can be applicable if the users' application can tolerate the relatively large delay between source and destination. Furthermore, the applicability of the bandwidth renegotiation method is also validated. © 1997 by John Wiley & Sons, Ltd.

Architecture and performance of a MAC protocol for the HFC system

Abstract: The IEEE 802.14 standard committee is currently working on a project to find a cost-effective means of providing access to integrated networks for people to enjoy multimedia programs and to work at home. An advanced system based on the cable TV system called hybrid fibre coax (HFC) is being studied. Since some properties of the HFC system preclude the possibility of directly using existing medium access control (MAC) protocols for its data link layer, a MAC scheme based on time division is discussed in this paper. This MAC scheme can be extended for wireless networks. © 1997 John Wiley & Sons, Ltd.