Richard A. Thompson

The dilated slipped Banyan switching network architecture for use in an all-optical local-area network

A modification of the classical banyan switching network architecture, called the dilated slipped banyan, is described. This architecture is recursive and switching networks of any size perform permutation switching under a simple switching rule. They also exhibit column-control and dilation, properties that are particularly relevant to guided-wave and free-space photonic technologies. A photonic switching network, with this dilated slipped banyan architecture, is proposed as the hub of an all-optical active-star local-area network. The switching assignment at this hub is time-multiplexed on a fixed schedule that is known to all the terminals. This all-optical local-area network provides the equivalent of full-connectivity with high simultaneous data rates between every pair of terminals. A 16-terminal local-area network with 100 Mb/s of contention-free bandwidth between every pair of terminals is described. >

The double-layer network architecture for photonic switching

This paper introduces a new architecture for strictly nonblocking multistage photonic space networks implemented using the switched directional couplers. This switching architecture has the lowest path loss and the best SNR performance of any nondilated network. The architecture can also be dilated, giving it even better SNR. >

An analysis of time-synchronized optical burst switching

Optical burst switching (OBS) is a competitive solution for all-optical next-generation networks. This paper describes a variation of OBS called time-synchronized optical burst switching (SynOBS), which utilizes a synchronized time-slotting technique in order to achieve better resource utilization than traditional OBS. Several resource reservation algorithms for SynOBS are discussed, along with their mathematical analyses, which are validated by simulation models. Finally, the performance of simulated SynOBS and traditional OBS is compared

Adaptive Speech Quality Management in Voice-over-IP Communications

The quality of VoIP communication relies significantly on the network that transports voice packets because this network does not usually guarantee available bandwidth, delay, and loss that are critical for real-time voice traffic. The solution proposed here is to manage a voice-over-IP stream dynamically, changing encoding parameters as needed to assure quality. The paper proposes an adaptive-rate control algorithm that establishes interaction between a VoIP sender and a receiver, and manages voice quality in real-time. Simulations demonstrate that the system provides better average communications quality than traditional fixed-rate VoIP.

Optimal timeslot size for synchronous optical burst switching

Traditional Optical Burst Switching (OBS) protocols assume that data bursts arrive at a given node asynchronously and that burst size varies, which causes a relatively inefficient utilization of the outgoing wavelengths. Time-Synchronized Optical Burst Switching (SynOBS) was proposed to overcome this ineffective resource utilization by utilizing a synchronized timeslot-based mechanism in the OBS network. However, while synchronization improves resource utilization over traditional OBS, the system must be carefully designed in order to achieve the best performance possible. This paper investigates the effect of timeslot size on the performance of SynOBS and proposes an analytical framework for approximating the optimal solution, based on the network configuration and input traffic characteristics.

Active delay and loss adaptation in overlay multicast tree

In this paper, the adaptive overlay multicast (AOM) protocol is presented, which is specially beneficial to long-lasting, large data distribution applications with large receiver sets. AOM distinguishes itself from the previous research with the following characteristics: (1) scalable overlay multicast tree construction method and a scoping technique to decrease overhead, (2) active adaptation to dynamic network conditions, and (3) efficient loss measurement and adaptation algorithms. We present extensive simulations of AOM including real Internet data and compare it with a HMTP-like protocol. The results show that AOM builds high-quality trees and adapts well to the network conditions while incurring low overhead.

Operational domains for circuit- and packet-switching

The performance of circuit-switched and of packet-switched networks are portrayed as surfaces in a three-dimensional evaluation space. The intersection of these surfaces defines two operational domains-one optimal for circuit-switching and one for packet-switching. This result is applied to network planning in future operational domains.

Optimal Combination of Circuit and Packet Switching in Optical Core Networks

In this paper, we propose a method to optimally partition a networks net capacity into circuit and packet switched channels. In our approach, the packet/burst switched channels are modeled as overflow channels. The overflow occurs from a group of circuit switched primary channels, which are semi-permanently allotted to a traffic source. Such a network provides balance between the statistical multiplexing gains of packet/burst switched channels and the minimum switching complexity of the circuit switching paradigm. We apply our design approach to optical core networks in which the complexity of packet/burst schemes are balanced with the cheap bulk carrying capacity of circuit switched channels. The blocking performance of various combinations of primary and overflow channels is analyzed and discussed, and optimized.

Photonic Timeslot Interchangers with a Reduced Number of Feed-forward Fiber Delay Lines

Abstract Time Division Multiplexing has been employed for decades in backbone networks. However, time channels have yet to be switched in the optical domain. The conventional time-switching method is to convert a signal from the optical to electrical domains before the switching operation is performed using electronic timeslot interchangers (TSI). Many proposed photonic timeslot interchangers (PTSI) have been published, but they are yet to be commercialized. One proposed model 1 claims to perform PTSI without blocking under a given component-count, but the claim was not verified or proven. This paper describes a simulation of that proposed model and verifies their claim. However, this paper proves that the originally-assumed component-count was over-estimated.

Computational quality model for wideband voice-over-IP communications

The E-model is a computational tool standardized by the ITU and developed to estimate the quality of VoIP communications. The objective of this model is to determine a voice quality rating that incorporates the quality of encoding processes and the mouth-to-ear characteristics of a path along a given call. The model was originally developed for narrowband 4-kHz telephony. This paper discusses a new methodology for extending the E-model to wideband 7-kHz communications.