Performance Enhancements for Asynchronous Random Access Protocols over Satellite

In this paper, a novel enhancement of the well known ALOHA random access mechanism is presented which largely extends the achievable throughput compared to traditional ALOHA and provides significantly lower packet loss rates. The novel mechanism, called Contention Resolution - ALOHA (CRA), is based on transmitting multiple replicas of a packet in an unslotted ALOHA system and applying interference cancellation techniques. In this paper the methodology for this new random access technique is presented, also w.r.t. existing Interference Cancellation (IC) techniques. Moreover numerical results for performance comparison with state of the art random access mechanisms, such as Contention Resolution Diversity Slotted ALOHA (CRDSA) are provided. Finally the benefit of taking strong forward error correcting codes for the performance of CRA is shown

Performance enhancements for algebraic soft decision decoding of Reed-Solomon codes

In an attempt to determine the ultimate capabilities of the Sudan-Guruswami-Sudan-Kotter-Vardy algebraic soft decision decoding algorithm for Reed-Solomon codes, we present a new method, based on the Chernoff bound, for constructing multiplicity matrices. In many cases, this technique predicts that the potential performance of ASD decoding of RS codes is significantly better than previously thought

In situ method for power re-equalization of wavelength pulses inside of OCDMA codes

A simple in-situ method to equalize power among individual wavelengths pulses representing two-dimensional wavelength-hopping time-spreading OCDMA code originally generated by a fibre Bragg grating-based OCDMA encoder is presented. Experimental data obtained in a field-based multiuser OCDMA testbed shows that applying this method results in system performance enhancements which was demonstrated by observing improved bit error rate (BER) during the field trials

Performance Enhancements of Ranging Radio Aided Navigation

Determining the position of team members is always useful information, whether it is a team of firefighters fighting a blaze or combatants clearing a building in the field. This information becomes even more decisive for the people responsible for their safety. To accomplish this in areas denied Global Navigation Satellite System (GNSS), such as around buildings or in steep valleys, alternative methods must be used. Radio ranging systems have been a part of the navigation solution for years. They unfortunately have poor performance in certain areas, such as inside buildings, due to multipath and other errors. To improve the position estimate it is believed that using vision, consumer grade inertial navigation systems, and any other measurement available can aid the navigation solution. To accomplish this, an extended Kalman filter was developed. It was configured as a centralized filter. This produced a baseline, showing that as image measurements were added, the navigation solution did improve. To simulate this with multiple vehicles and/or soldiers required a large state vector for the Kalman filter. To manage the large number of states and efficiently incorporate them into influence matrices, a Rosetta stone was designed for state management. This Rosetta stone breaks the states into simpler blocks such as position and attitude for the soldier and position for the image features. This in turn made updating the influence matrix and covariance matrix a smoother process. The impact of adding image measurements has been two fold. First, the position RMS errors were reduced by approximately a factor of 2. Second, the attitude which fluctuated greatly in the radio only cases was reduced by a factor of 10 through image aiding

Super-resolution Line Spectrum Estimation with Block Priors

We address the problem of super-resolution line spectrum estimation of an undersampled signal with block prior information. The component frequencies of the signal are assumed to take arbitrary continuous values in known frequency blocks. We formulate a general semidefinite program to recover these continuous-valued frequencies using theories of positive trigonometric polynomials. The proposed semidefinite program achieves super-resolution frequency recovery by taking advantage of known structures of frequency blocks. Numerical experiments show great performance enhancements using our method.Comment: 7 pages, double colum

An improved simulated annealing algorithm for standard cell placement

Simulated annealing is a general purpose Monte Carlo optimization technique that was applied to the problem of placing standard logic cells in a VLSI ship so that the total interconnection wire length is minimized. An improved standard cell placement algorithm that takes advantage of the performance enhancements that appear to come from parallelizing the uniprocessor simulated annealing algorithm is presented. An outline of this algorithm is given

Multiplexing systems performance enhancements with all-optical signal processing

It is believed that an all-optical signal processing based on advanced integrated devices (passive, active or both) would play an important role in future multiplexing systems. In this paper we discuss approaches and techniques we have developed and demonstrated for improving the scalability and performance of Optical Code Division Multiplexing (OCDM)