David E. Robillard | Searcharxiv

arXiv2013

Adaptive Software Radio Steganography

This paper presents an adaptable steganography (information hiding) method for digital radio communication. Many radio steganography methods exist, but most are defined at higher levels of the protocol stack and are thus protocol dependent. In contrast, this method is defined at the physical layer, which makes it widely applicable regardless of the protocols used at higher layers. This approach is also adaptive; the covertness of the hidden channel is simple to control via a single continuous parameter either manually or automatically. Several variations are introduced, each with performance evaluated by simulation. Results show this to be a feasible method with a reasonable trade-off between performance and covertness.

cs.MM↗

arXiv2010

Practical Parallel External Memory Algorithms via Simulation of Parallel Algorithms

This thesis introduces PEMS2, an improvement to PEMS (Parallel External Memory System). PEMS executes Bulk-Synchronous Parallel (BSP) algorithms in an External Memory (EM) context, enabling computation with very large data sets which exceed the size of main memory. Many parallel algorithms have been designed and implemented for Bulk-Synchronous Parallel models of computation. Such algorithms generally assume that the entire data set is stored in main memory at once. PEMS overcomes this limitation without requiring any modification to the algorithm by using disk space as memory for additional "virtual processors". Previous work has shown this to be a promising approach which scales well as computational resources (i.e. processors and disks) are added. However, the technique incurs significant overhead when compared with purpose-built EM algorithms. PEMS2 introduces refinements to the simulation process intended to reduce this overhead as well as the amount of disk space required to run the simulation. New functionality is also introduced, including asynchronous I/O and support for multi-core processors. Experimental results show that these changes significantly improve the runtime of the simulation. PEMS2 narrows the performance gap between simulated BSP algorithms and their hand-crafted EM counterparts, providing a practical system for using BSP algorithms with data sets which exceed the size of RAM.

cs.DC↗