Showing papers by "Shivendra S. Panwar published in 2001"

On the performance of a dual round-robin switch

Abstract: The dual round-robin matching (DRRM) switch has a scalable, low complexity architecture which allows for an aggregate bandwidth exceeding 1 Tb/s using current CMOS technology. In this paper we prove that the DRRM switch can achieve 100% throughput under i.i.d. and uniform traffic. The DRRM is the first practical matching scheme for which this property has been proved. The performance of the DRRM switch is then studied and compared with the iSLIP switch. The delay performance under uniform traffic and the hot-spot throughput of DRRM is better than that of iSLIP, while the throughput of iSLIP under some nonuniform traffic scenarios is slightly higher than that of DRRM. Since throughput drops below 100%, under nonuniform traffic, we also examine some variations of the DRRM matching scheme for nonuniform traffic.

Reliable transmission of video over ad-hoc networks using automatic repeat request and multipath transport

Abstract: The increase in the bandwidth of the wireless channels and the computing power of the mobile devices makes it possible to offer video service for wireless networks in the near future. In an ad-hoc network, strong error protection is required because of the lack of a fixed infrastructure. On the other hand, the mesh structure of an ad-hoc network implies that there may be multiple paths existing between a source and destination, which can be used to enhance video transmissions. We propose a simple but robust scheme for reliable transmission of video in bandwidth limited ad-hoc networks. In our scheme, a video stream is layer coded. The base layer (BL) packets and the enhancement layer (EL) packets are transmitted separately on two disjoint paths using multipath transport (MPT). BL packets are protected by automatic repeat request (ARQ), and a lost BL packet is retransmitted through the path where EL packets are transmitted. An EL packet has lower priority than a retransmitted BL packet and may be dropped at the sender when congestion occurs. Simulation results show that this scheme can guarantee a graceful video quality in adverse channel conditions. It is effective for video transmission over the high loss environment found in ad-hoc networks.

A reference picture selection scheme for video transmission over ad-hoc networks using multiple paths

Abstract: Enabling video transmission over ad-hoc networks is more challenging than over conventional mobile networks because a connection path in an ad-hoc network is highly error-prone and the path can go down frequently. On the other hand, it is possible to establish multiple paths between a source and a destination, which provides an extra degree of freedom in coding algorithm design. This paper presents a feedback-based reference picture selection scheme for video transmission over ad-hoc networks. Encoded video streams are transmitted over multiple paths and the reference frames for motion compensated prediction are selected according to the feedback information about the paths’ condition. Simulations under the two paths scenario have shown significant improvement over two standard techniques, layered coding and video redundancy coding, which do not use feedback. A novel statistical model for the ad-hoc multi-path environment is also proposed and used in our simulation of transmission loss.

File distribution in networks with multimedia storage servers

Abstract: In this paper, we consider a problem in networks with storage servers for providing multimedia service. The design involves assigning communication link capacity, sizing the multimedia servers, and distributing different types of content at each server, while guaranteeing an upper limit on the individual end-to-end blocking probability. We consider alternative methods for obtaining the end-to-end blocking probability with low computation time and present optimization procedures to obtain an optimal solution. Under a linear cost structure, our numerical investigations consider different scenarios that might be helpful in understanding how to distribute multimedia content for a cost-optimized solution. © 2001 John Wiley & Sons, Inc.

Analysis of TCP congestion control using a fluid model

Abstract: We develop an analytical fluid model for TCP Reno based on delay differential equations. Using this model, we have developed a prototype for a fluid based simulation tool for TCP. We empirically validate this model by matching the window, throughput and queue evolution curves obtained from the model to that offered by a simulation output. We claim that this analytical model provides the basis for an analyzer that can complement simulators that perform a packet by packet simulation.

The effective bandwidth of Markov modulated fluid process sources with a generalized processor sharing server

Abstract: Generalized processor sharing (GPS) is an important scheduling discipline because it enables bandwidth sharing with work conservation and traffic isolation properties. While Markov modulated fluid processes (MMFP) capture the dynamics of the sources, the analysis of such sources with a GPS server is difficult because of the large state space. We study a multi-queue GPS system with MMFP classes and propose a scalable, low complexity algorithm for the tail distributions of the logical queues. The effective bandwidth of the classes and a simple connection admission control (CAC) scheme are derived. Numerical results illustrate the efficiency and accuracy of the technique. The application to an example system of classes consisting of voice and variable bit rate (VBR) video traffic is included.

GPS analysis of multiple sessions with applications to admission control

Abstract: We introduce a statistical method to analyze multiplexing of multiple sessions sharing link bandwidth using generalized processor sharing (GPS) scheduling. Our method is shown to substantially improve previous upper bounds for GPS scheduling of Markov modulated fluid processes (MMFP) sessions, especially as the number of sessions increases. Application of analytical results to admission control indicate that by sharing bandwidth using GPS among traffic classes there are significant gains over systems that statically segregate the link bandwidth. This effect is quantified in several experiments where various combinations of source types are used. The gains are pronounced when bursty sources with stricter QoS requirements are used.

Data sequencing method to improve transmission of self-similar data in a multi-node network

Abstract: The present invention is a data formatting method for data in a digital communication network. The first step in the method is to identify a predetermined number of blocks in the data stream, each block including several data values. The blocks are shuffled by skipping a number of blocks of the input data between consecutive blocks of transmitted data and periodically resetting the skip pointer to transmit the skipped blocks as a part of a later skip operation. The shuffled blocks are then transmitted through the network and reordered again at the other side to recreate the original data stream. Others blocks are similarly reordered and transmitted. The shuffling of the blocks of data reduces long-term dependency in the data while maintaining local order.