Nitin Gogate

Supporting image and video applications in a multihop radio environment using path diversity and multiple description coding

This paper examines the effectiveness of combining multiple description coding (MDC) and multiple path transport (MPT) for video and image transmission in a multihop mobile radio network. The video and image information is encoded nonhierarchically into multiple descriptions with the following objectives. The received picture quality should be acceptable, even if only one description is received and every additional received description contributes to enhanced picture quality. Typical applications will need a higher bandwidth/higher reliability connection than that provided by a single link in current mobile networks. To support these applications, a mobile node may need to set up and use multiple paths to the desired destination, either simply because of the lack of raw bandwidth on a single channel or because of its poor error characteristics, which reduce its effective throughput. The principal reason for considering such an architecture is to provide high bandwidth and more robust end-to-end connections. We describe a protocol architecture that addresses this need and, with the help of simulations, we demonstrate the feasibility of this system and compare the performance of the MDC-MPT scheme to a system using layered coding and asymmetrical paths for the base and enhancement layers.

Supporting video/image applications in a mobile multihop radio environment using route diversity

This paper investigates the need for multiple path transport (MPT) of video and image information in a multihop mobile radio network. The video and image information is encoded non-hierarchically into a multiple description coding (MDC) with the following objectives. The received picture quality should be acceptable even if only one description is received and every additional received description contributes to enhanced picture quality. Typical applications will need a higher bandwidth/higher reliability connection than that provided by current mobile networks. For supporting these applications a mobile node may need to set up and use multiple paths to the desired destination either simply because of the lack of raw bandwidth on a single channel or because of its poor error characteristics which reduces its effective throughput. In the context of this work, the principal reasons describe a protocol architecture that addresses this need and with the help of simulations, we demonstrate the feasibility of this system and compare the performance of the MDC-MPT scheme to that of a hierarchical coding scheme.

On a resequencing model for high speed networks

The authors analyze the effect of fixed delay in conjunction with queueing and resequencing delay on the optimal distribution of traffic on multiple disjoint paths. They study a system of two hosts or end nodes, connected by a high speed network communicating on two virtual channels which follow disjoint physical paths. The paths have a different number of hops and/or physical length which leads to a different amount of constant delay for each of them. The variable delay on each path is modelled by a queue with exponential service. Furthermore the destination node delivers packets an the order they arrived at the source node, which entails additional resequencing delay. They find the optimal split of traffic, so as to minimize the total average system time (including the resequencing delay). The results show that the optimal splitting probability may be heavily dependant on the difference in the fixed delays on the two paths. Numerical examples are presented to illustrate the effect of fixed delay on the fraction of traffic routed to different paths. Performance can be further improved when they do a deterministic split of the traffic.<<ETX>>

Assigning customers to two parallel servers with resequencing

We consider the resequencing delay characteristics of a system with two heterogeneous servers serving a single queue with Poisson packet arrivals. An ordered delivery of packets is guaranteed at the receiver, hence packets arriving out of order suffer additional resequencing delay. We introduce the concept of threshold policies with variable routing positions and obtain analytical expressions for the end-to-end delay. With numerical examples we show that some improvement is obtained in the end-to-end delay values with variable routing position policies over fixed position routing policies. Further, initial simulation studies seem to indicate that this observation is true even with bursty arrivals.

Supporting applications in a mobile multihop radio environment using route diversity. I. Non-real time data

This paper motivates the need for the multiple path transport (MPT) of information in a multihop mobile radio network for supporting non-real time applications. Typical applications will need a higher bandwidth/higher reliability connection than that provided by current mobile networks. For supporting these applications a mobile node may need to set up and use multiple paths to the desired destination, either simply because of the lack of raw bandwidth on a single channel or because of its poor error characteristics, which reduces its effective throughput. In the context of this work, the principal reasons for considering such an architecture are providing high bandwidth and a more robust end-to-end connection. We describe a protocol architecture that addresses this need and, with the help of simple simulation models, we show that the delay and throughput performance of multiple path schemes is significantly better than that of a conventional scheme in which one session makes use of one path. For the data applications considered in this work, there is an additional advantage of security because tapping any one path does not give access to the complete information.

Simulation study of a fixed wireless access system

This paper describes a fixed wireless local loop (FWLL) system designed to provide data and voice services to fixed users. The FWLL system uses electronically steerable base-station (BS) antennas that generate multiple narrow beams which hop around when communicating with terminals. The multiple access is provided by TDMA and the up/downlinks operate in a frequency division duplex (FDD) mode. The same frequency band is reused in all the cells. With the help of simulations we evaluate the systems capacity which, in this context, is the number of serviceable terminals per cell for a given percentage of terminals that exceed a preset signal to interference ratio (SIR). We also study the effect of various antenna parameters on the systems capacity. We show an improvement in capacity if a terminal has the ability to communicate with the BS to which it has the least path-loss instead of being required to always communicate with the BS located geographically closest.