Implementation issues in source coding

An edge preserving image coding scheme which can be operated in both a lossy and a lossless manner was developed. The technique is an extension of the lossless encoding algorithm developed for the Mars observer spectral data. It can also be viewed as a modification of the DPCM algorithm. A packet video simulator was also developed from an existing modified packet network simulator. The coding scheme for this system is a modification of the mixture block coding (MBC) scheme described in the last report. Coding algorithms for packet video were also investigated

Hysteretic Control Technique for Overload Problem Solution in Network of SIP Servers

This paper contains research and development results concerning application of hysteretic control principles to solve SIP servers overload problem, which is known from a number of IETF standards and scientific papers published over the past few years. The problem is that SIP protocol, being the application layer protocol, by default has no build-in means of overload control, as, for example, SS7, MTP2 and MTP3 protocols. It was the SS7 network, where a threshold mechanism of hysteretic signalling load control was first implemented. In this paper we describe the main up-to-date solutions of an overload control problem in a signalling network, and develop analytical models of hysteretic control, which are useful in the development of load management functions of SIP servers. We also propose the design of Open SIP signalling Node (OSN) software architecture which is intended to be used for simulations and comparison of various overload control mechanisms

The Mx/G/1 queue with queue length dependent service times

We deal with the MX/G/1 queue where service times depend on the queue length at the service initiation. By using Markov renewal theory, we derive the queue length distribution at departure epochs. We also obtain the transient queue length distribution at time t and its limiting distribution and the virtual waiting time distribution. The numerical results for transient mean queue length and queue length distributions are given.Bong Dae Choi, Yeong Cheol Kim, Yang Woo Shin, and Charles E. M. Pearc

An Adaptive Redundancy Reduction Technique

In telemetry systems, the limited power available from the RF transmitter imposes a constraint on the data transmission rate. For example, a spacecraft’s ability to communicate with a ground receiving station decreases with the square of the distance, and electrical power to operate the system increases with the data transmission rate. To solve this problem, considerable attention has been devoted toward improving the efficiency of telemetry systems by selecting advantageous coding, modulation and reconstruction techniques. One technique which is used to achieve this goal is to design a telemetry system which transmits only the significant information contained in the source data instead of transmitting all of the data so that the system capacity is maximized while the power requirements and size of the system is minimized. This technique is called data compression. Data compression reduces the bandwidth needed to transmit a given amount of information in a given time or it can reduce the time needed to transmit a given amount of information in a given bandwidth. While basic data compression techniques have been applied for many years in the off-line processing of data and by human analysts in seeking significant changes in data, their application to on-line service and particularly to space vehicles has been quite recent. Such compression must be accomplished without sacrificing the information requirements of the user. The performance enhancement of a basic data acquisition system by incorporation of data compression can be manifested in a variety of ways, depending on the manner in which the data compressor is utilized in the system and the performance desired. As shown in Figure 1-1, the engineer had the option of incorporating the data compression into either the transmitter or the receiver portions of the system. Four basic categories of data handling come under this definition: parameter extraction, adaptive sampling, redundancy reduction and coding. Figure 1-2 shows a schematic classification of data compression techniques by category

A programmable structure for pervasive computing

This exstended abstract presents an asymmetric and programmable (extensible) approach to pervasive computing. The idea is to off-load computations from light portable clients into a back-bone of seamlessly integrated servers. This way, a user can extend and personalize his pervasive computational environment by installing computations following his trajectory throughout the day. Focus on this extended abstract is on structural issues related to the back-end servers running mobile code off-loaded from the mobile user

Delta modulation techniques for low bit-rate digital speech encoding

Includes bibliography.Two new hybrid companding delta modulators for speech encoding are presented here. These modulators differ from the Hybrid Companding Delta Modulator (HCDM) proposed by Un et al in that the two new encoders employ Song Voice Adaptation as the basis of the instantaneous compandor, rather than Constant Factor adaptation. A detailed analysis of the performance, both objective and subjective, of these hybrid codecs has been carried out. Results show that overall the two codecs developed as part of this project are better than the HCDM codec. In addition the new codecs offer simpler implementation in digital hardware than the HCDM. A Computer Aided Test (CAT) system has been developed to simplify the design and test processes for speech codecs

A study of data coding technology developments in the 1980-1985 time frame, volume 2

The source parameters of digitized analog data are discussed. Different data compression schemes are outlined and analysis of their implementation are presented. Finally, bandwidth compression techniques are given for video signals