In this study we investigate acquisition (code offset and channel state estimation) of multiple direct sequence spread spectrum DSSS signals in a multi-antenna ad hoc network. We derive the form of the optimal acquisition algorithm and show that it is NP-complete. We then derive a tractable suboptimal approach where we use a successive multistage cancellation approach in estimating the initial ...

Wireless networking is rapidly growing and becomes an inexpensive technology which allows multiple users to simultaneously access the network and the internet while roaming about the campus. In the present work , the software development of a wireless LAN(WLAN) is highlighted. This WLAN utilizes direct sequence spread spectrum (DSSS) technology at 902MHz RF carrier frequency in its physical lay...

This work concentrates on the problem of watermarking embedding and optimum detection in color images through the use of spread spectrum techniques, both in space (Direct Sequence Spread Spectrum or DSSS) and frequency (Frequency Hopping). It is applied to RGB and opponent color component representations. Perceptive information is considered in both color systems. Some tests are performed in or...

Heterogeneous Distributed Storage Systems (DSSs) are close to the real world applications for data storage. Each node of the considered DSS, may store different number of packets and each having different repair bandwidth with uniform repair traffic. For such heterogeneous DSS, a failed node can be repaired with the help of some specific nodes. In this work, a family of codes based on graph the...

Recent research on distributed storage systems (DSSs) has revealed interesting connections between matroid theory and locally repairable codes (LRCs). The goal of this chapter is to introduce the reader to matroids and polymatroids, and illustrate their relation to distribute storage systems. While many of the results are rather technical in nature, effort is made to increase accessibility via ...

This work concentrutes on the problem of wutermurking embedding und optimum detection in color imuges through the use of spread spectrum techniques, both in spuce (Direct Sequence Spread Spectrum or DSSS) and fiequency (Frequency Hopping). It is applied to RGB und opponent color component representutions. Perceptive information is considered in both color systems. Some tests are performed in or...

Due to the varying rates of change of ephemeral administrative and enduring clinical knowledge in decision support systems (DSSs), the functional partition of knowledge base (KB) components can lead to more efficient and cost-effective system implementation and maintenance. Our prototype loosely couples a clinical event monitor developed by Columbia University Medical Center (CUMC) with a secur...

This paper describes a modification of the backoff mechanism for IEEE 802.11 networks. The efficiency of the modified backoff mechanism compared to that is currently used in the standard was analyzed. The realized throughput and the mean packet delay for DSSS and FHSS physical layers for different number of stations were determined. The overall rate of collisions that occurred during transmissi...