Development of a Software-Defined Underwater Acoustic Communication System

This report started with a brief history and recent development of underwater acoustic communication systems as well as software-defined radio technologies. Then, some challenges from underwater acoustic channels and available underwater acoustic communication modems are discussed. After finished introducing the basics of SDR and GNU Radio, a detailed description of implementing a software-defined acoustic communication system in GNU Radio are presented, along with some key concepts of the system. Then, some hardware specifications are presented, following by detailed documentation on a software-defined acoustic communication system experiment with a host computer, a USRP, an acoustic hydrophone, and a hydrophone. At the end of Section 4, the results of the experiment are discussed. Lastly, the conclusions of this report are made. Some possible directions for future work are suggested in Section 6

Extreme rays of the (N,k)(N, k)-Schur Cone

We discuss several partial results towards proving Dennis White's conjecture on the extreme rays of the $(N,2)$-Schur cone. We are interested in which vectors are extreme in the cone generated by all products of Schur functions of partitions with $k$ or fewer parts. For the case where $k =2$, White conjectured that the extreme rays are obtained by excluding a certain family of "bad pairs," and proved a special case of the conjecture using Farkas' Lemma. We present an alternate proof of the special case, in addition to showing more infinite families of extreme rays and reducing White's conjecture to two simpler conjectures.Comment: This paper has been withdrawn by the authors due to a misinterpretation of the generalized Littlewood-Richardson rule in several proof

A mutual authentication and key update protocol in satellite communication network

Satellite communication networks have been widely used to provide essential communication services, including voice communication, global positioning, message communication, etc. However, sorts of network attacks are easy to be launched in these networks due to the limited computation capability and communication width, long communication delay, and intermittent link connection. In this paper, we first propose a new [E]ncryption-based [M]utual [A]uthentication and [K]ey [U]pdate (EMAKU) protocol in satellite communication networks. Next we analyze the security of the EMAKU protocol under two classic network attacks which are replay attack and man-in-the-middle attack. Finally, experiments show that the EMAKU protocol is 21.5% faster than the traditional encryption-based authentication protocols, and the average time of key update of the EMAKU protocol is about 450.01 ms

Polychromatic drivers for inertial fusion energy

Although tremendous achievements have been made toward inertial confinement fusion, laser plasma instabilities (LPIs) remain to be an inevitable problem for current drive schemes. To mitigate these instabilities, significant efforts have been paid to produce high-power broadband ultraviolet lasers. However, no practical scheme has been demonstrated up to now for efficient triple-frequency conversion of broadband laser. Here we propose the design of polychromatic drivers for the generation of multicolor beams mainly based upon the optical parametric amplification, which can significantly enhance the third-harmonic conversion efficiency. Each polychromatic light has four colors of monochromatic beamlets with a full spectrum width of 3\%, and the beamlet colors of any two adjacent flanges are different. The suppression effects of such polychromatic lights have been investigated via large scale particle-in-cell simulations, which indicate that more than 35\% of the incident energy can be saved from the LPIs compared with monochromatic lasers for the direct-drive scheme, or high-density filled target for the indirect-drive scheme. The proposed polychromatic drivers are based on the matured technologies, and thus may pave the way towards realization of robust and high-efficiency fusion ignition