Real-time data assimilative modeling on Georges bank

Real-time oceanic forecasts were constructed at sea on Georges Bank during Spring 1999. Ship- and shore-based computations were combined to deliver daily 3-day forecasts to shipboard scientists for interpreting observations and planning operations. Data assimilated included acoustic Doppler current profiler velocities, drifter trajectories, and taxa-specific plankton observations from a Video Plankton Recorder (VPR) system. Services provided included basic 3-D circulation forecasts, forecast positions of drifters, dye and zoo-plankton, and the advective adjustment of observations to produce synoptic maps. The results indicate that real-time, at-sea data assimilative modeling can provide valuable information services and can be deployed routinely, provided that networking among ships, instruments, and shore continues to improve. This paper summarizes the real-time modeling experience. Results of the larger effort including scientific data interpretation are being reported separately

M.: On randomized broadcasting and gossiping in radio networks

Abstract. This paper has two parts. In the first part we give an alternative (and much simpler) proof for the best known lower bound of Ω(D log (N/D)) time-steps for randomized broadcasting in radio networks with unknown topology. In the second part we give an O(N log 3 N)time randomized algorithm for gossiping in such radio networks. This is an improvement over the fastest previously known algorithm that works in time O(N log 4 N).

Algebraic Constructions for PSK Space-Time Coded Modulation

. We consider the design of phase shift keyed space-time coded modulation for two antenna systems based on linear codes over rings. Design rules for constructing full diversity systematic space-time codes based on underlying existing algebraic codes were first presented by Hammons and El Gamal in 2000. We reformulate and simplify these design rules, resulting in the condition that the characteristic polynomial of the parity generation matrix must be irreducible. We further extend the results to non-systematic codes. These results yield a recursive construction based on the Schur determinant formula. The resulting block codes are guranteed to provide full diversity advantage. In addition, the code construction is such that the corresponding parity check matrix is sparse, enabling the use of the powerful Sum-Product algorithm for decoding.