Jeremiah F. Hayes

Modeling and analysis of telecommunications networks

Preface. Retrieving Files from the Wiley FTP and Internet Sites. 1. Performance Evaluation in Telecommunications. 2. Probability and Random Processes Review. 3. Application of Birth and Death Processes to Queueing Theory. 4. Networks of Queues: Product Form Solution. 5. Markov Chains: Application to Multiplexing and Access. 6. The M/G/1 Queue: Imbedded Markov Chains. 7. Fluid Flow Analysis. 8. The Matrix Geometric Techniques. 9. Monte Carlo Simulation. Index.

Performance analysis of a multicast switch

The performance of a multicast switch, a space division switch in which a packet at an input port is routed to a subset of the output ports, is discussed. The delay under the assumption of input port buffering is determined. The system is modeled as an independent set of M/G/1 queues. A key assumption in the analysis is that output port contention is settled by random selection among the contending input ports. In order to justify this as well as the other assumptions, a Monte-Carlo simulation of the system is devised. Numerical results from the analysis and simulation of the system are presented. >

Research: Admission-control techniques with application to broadband networks

This paper contains an exact analysis of the blocking conditions at the burst level, experienced by different types of traffic in an ATM network. A basic assumption is that traffic is generated by a finite set of independent two-state sources that share equally the available bandwidth. When all sources are active the bandwidth demanded may exceed the capacity of one or more links in the network. In this paper, we show, using reversibility arguments, that the product-form solution is valid for our model. Then we give a recursion that reduces the multidimensional birth-death process of our original model into a one-dimensional birth-death like system. Thus, we calculate burst blocking probabilities by means of a recursive relation that considerably simplifies the complexity of the problem. The analysis is extended to a two-dimensional case that models a switch, and a similar recursion is suggested. The above results supply the analytical basis for an admission control mechanism that guarantees a predefined performance threshold (in terms of burst loss probability) for the classes of traffic supported.

Performance comparison of two input access methods for a multicast switch

A comparison of the performance of two input access mechanisms for multicast switching is presented. The first of these-a cyclic priority input access method-is a derivative of the ring token reservation method which eliminates the unfairness of the ordinary ring token reservation. It has the advantage of being relatively simple and easy to implement. A second approach employs a neural network to resolve output port conflict. While more difficult to implement, it has a delay-throughput performance advantage over the cyclic priority approach. The primary performance measurements are the switch throughput and the packet delay. A key assumption is that all copies of the same packet must be switched in the same slot. >

Traffic analysis of a local area network with a star topology

Two forms of fast circuit switching are modeled and studied through mathematical analysis and Monte Carlo simulation. The two examples described use the switching technique in an optical-fiber-based local area network with a star topology. The technique is compatible with time-division multiplexing techniques that are used for a range of traffic classes. Further, the technique trades transmission capacity for processing power, which is the critical limitation of the system. By means of a certain independence assumption, the first form of fast circuit switching is modeled as an M/G/1 queue. The results of the analysis show excellent agreement with simulation. The general result is that there is good system throughput, despite simplicity of processing. The second form, in which rather than first-come first-served the discipline is to search for a message whose destination queue is free, is studied by means of simulation alone. The results indicate an improved performance with a modest increase in processing power. >

Access control in multicast packet switching

Access control and performance for multicast packet switching in a broadband network environment are studied. In terms of scheduling the transmission of the copies of the packet onto output ports, two basic service disciplines are defined: one-shot scheduling (all the copies transmitted in the same time slot) and call splitting (transmission over several time slots). As subcategories of call splitting, SS (strict-sense) specifies that each packet can send at most one copy to the destination per time slot, whereas WS (wide-sense) does not carry this restriction. A scheme called revision scheduling, which mitigates the head-of-line (HOL) blocking effect by sequentially combining the one-shot scheduling and the call splitting disciplines, is proposed. Output contention resolution implementations, in the form of combinational logic circuits designed to resolve output contentions arising in each of the call scheduling disciplines, are introduced. A neural-network-based contention resolution algorithm is proposed to demonstrate the improvement of the optimal scheduling. >

Call scheduling in multicasting packet switching

The implementation and performance of multicast packet switching in a broadband network environment are discussed. In terms of scheduling the transmission of the copies of the packet onto output ports, two basic service disciplines have been defined: (1) one-shot scheduling where all the copies are transmitted in the same time slot; and (2) call splitting with transmission over several time slots. As subcategories of call splitting strict-sense call splitting specifies that each packet can send at most one copy to the destination per time slot and wide-sense call splitting does not carry this restriction. A novel scheme called revision scheduling is proposed to mitigate the head of line blocking effect by sequentially combining the one-shot scheduling and the call splitting disciplines. Schematic structures are introduced for each category of scheduling, in the form of combinational logic circuits which are designed to resolve the output contentions corresponding to call scheduling disciplines, by incorporating a cyclic priority access policy. To compare the performances of various techniques, simulation studies were performed.<<ETX>>

Performance of a priority-based dynamic capacity allocation scheme for wireless ATM systems

The performance of a priority-based dynamic capacity allocation suitable for wireless ATM systems is presented. The scheduling of ATM cell transmission in each uplink TDMA frame is based on a priority scheme with priority given to real-time traffic over nonreal-time traffic. Real-time traffic exceeding the uplink capacity is lost while nonreal-time traffic that cannot be served is stored in a first-in first-out (FIFO) queue. An analytical model is developed to evaluate the cell loss ratio (CLR) of both real-time and nonreal-time traffic. Aggregate voice, video, and data traffic is modeled by three two-state Markov-modulated Poisson processes (MMPPs). Analytical results for different system capacities and various traffic loads and scenarios are discussed. Simulation results with on-off sources and approximating MMPP sources are also presented.

Performance analysis of cyclic-priority input access method for a multicast switch

A study of the performance of a cyclic-priority input access mechanism for a multicast switch is carried out. The method is a derivative of the ring token reservation method which eliminates the unfairness of the ordinary ring token reservation. It has the further advantage of being simple and easy to implement. The primary performance measurements are the switch throughput and the packet delay. A key assumption is that all copies of the same packet must be switched in the same slot.<<ETX>>

The Effect of Antenna Physics on Fading Correlation and the Capacity of Multielement Antenna Systems

In this paper, we investigate the effects of antenna directivity and antenna orientation on fading correlation and, therefore, the channel capacity in multiple-input-multiple-output communication systems by means of a spherical simulation model. The correlation is caused by the mutual interaction of the scattering environment and antenna elements. To study the effect of antenna directivity and orientations on the correlation and channel capacity in a more realistic environment, we extend the ldquoone-ringrdquo model to a spherical scattering environment, which is appropriate for narrowband 3D Rayleigh fading. In our model, scatterers around a subscriber unit are distributed over a sphere centered on the antenna array in the subscriber unit. Antenna directivity is included in a precise way, and the antenna array can be placed in any orientation. Any type of antenna can be studied in the model. Through simulation, we find that directive antenna elements in linear broadside arrays make the channel capacity more strongly directive than when antenna elements are isotropic. Moreover, different antenna patterns and orientations have different outage capacities depending on the interaction of antenna directivities and the incident waves, which shows that the antenna pattern and orientation affect the channel capacity to some extent. In the uniformly scatter-rich environment, the microstrip antenna array can have 10% higher outage capacity than that of the dipole antenna array.